Folding roll-away tables having seating structures are know in the art, for example as disclosed in U.S. Pat. Nos. 6,223,661 and 3,075,809, the disclosures of both of which are hereby incorporated by reference. Such foldable tables have lifting assist mechanisms intended to assist an operator during the folding of a folding table from an unfolded use position to a folded storage or moving position. Existing lifting mechanisms typically use one or more torsion bars for providing lifting assistance to the operator. Two to four torsion bars are employed in a typical torsion bar lifting assist mechanism. The torsion bars are typically attached to the table frame on one end of the torsion bar and attached to a hinge tube of a leg assembly at the other end of the torsion bar. Each torsion bar stores energy that will be used to fold the table assembly. Torsion bar holders are attached to the table frame and have a hexagonal hole configuration that solidly accepts and locks one end of the torsion bar to the table frame assembly. In this manner, the attached torsion bar end is solidly positioned and not allowed to twist with respect to the table frame at this point. The opposite end of the torsion bar is solidly attached to the hinge tube of a leg assembly with a second hexagonal torsion bar holder. With this end of the torsion bar firmly attached to the leg assembly, the torsion bar will twist as the leg assembly rotates with respect to the table frame when the folding table assembly is unfolded between the storage and use positions. In existing foldable tables, the torsion bars typically twist or rotate throughout a range of ninety degrees (90°) during the unfolding or folding operation. Other lifting assist mechanisms using torsion bars may twist through a greater or lesser angular range depending on the torsion bar construction.
During the unfolding process of existing foldable table assemblies from a folded or storage position to an open unfolded use position, the operator unfolds the foldable table and thereby stores potential energy in the torsion bars. The operator-applied force and the force of gravity acting on the table assembly overcomes the natural tendency of the torsion bars to remain in an untwisted state as the table unfolds. As the table assembly unfolds, the free ends of the torsion bars are twisted through ninety (90) degrees as the table legs swing out to an open position and thereby store enough energy in the torsion bars to later release the stored energy to fold the table.
To initiate the folding process from an unfolded or use position to a closed or folded storage position, a small input force is required from the operator. The initial operator input force is necessary since the folding table tends to want to fold due to the stored energy in the torsion bars. The folding table assembly needs a locking mechanism to keep the folding table in a flat and unfolded use position. Typical foldable table designs, such as those described in U.S. Pat. Nos. 6,223,661 and 3,075,809, require a small operator input force of about ten (10) to twenty (20) pounds of force vertically applied at the midpoint of the foldable table assembly near the center hinge point to initiate the folding sequence.
Existing lifting assist torsion bar designs, however, have drawbacks associated with them. For example, the amount of force needed to close the table varies as it closes, so that more force is needed, either from the operator or the torsion bars, when the table begins to fold away from its unfolded use position than when it approaches the fully folded storage position. Existing designs attempt to provide the required force by attempting to balance the amount of torque induced by the torsion bars with the weight of the table as it is being folded or unfolded. However, if too much force is added near the top of the table's travel, the table will snap shut causing a potential safety hazard as well as unnecessary wear and tear. Further it would be difficult to pivot the two halves of the tables as an operator starts to unfold the table. If there is insufficient force near the top of the table's travel, the table will “feel” heavy as the operator tries to fold it. Thus, additional lifting force would be beneficial in assisting the operator at the beginning of the folding process but is not necessary at the end of the folding process as the table approaches its folded position.
Existing mobile folding tables typically have stool-style seat structures with wheeled casters positioned directly underneath the stool seat post of the end leg assembly, for example as disclosed in U.S. Pat. No. 3,075,809. In this end leg configuration, the casters always maintain contact with the floor irrespective of whether the folding table assembly is folded, unfolded or in a position therebetween. The tendency of the lifting assist torsion bar assembly is to fold the table from an unfolded position, thus the center legs will tend to rise off the floor. When the center legs rise and lose contact with the floor, so too do the gripping pads at the base of the seating stool tubes. This results in the weight of the table being shifted mostly to the wheeled caster which further results in movement or wandering of the unfolded table from its original location.
Additionally, if weight is concentrated near or at the ends of the folding table assembly or directly over the wheeled casters, the center legs also tend to rise off the floor, also resulting in movement or wandering of the unfolded table from its original location. Existing folding tables, having wheeled casters on the end leg assemblies are prone to shift or wander in the unfolded use position, especially on hard floor surfaces. This can be a significant problem in certain use environments such as in school cafeterias and the like where hard flooring surfaces such as vinyl tile is common. Further, manufacturing tolerances, clearances, and the inherent flexibility in the table structure increases the likelihood that the table will deviate or wander from its original unfolded location on the floor.
There is thus a need for a folding table assembly with a lifting assist mechanism that will provide an assist lifting force primarily during the beginning of the folding process of the foldable table assembly from an unfolded use position to a folded storage position. There is also a need for a mechanism that will assist in maintaining an unfolded table assembly in a stationary position and to prevent the unfolded table from wandering or deviating from its original location on the floor.